I have been trying to complete this quest for a half hour. Ended up giving up and heading to bed after this. I made it across several times on my Monk but did not get credit for it once. I tried landing in different spots on the platform and nothing changed. I tried relogging and nothing changed. Switched to my Hunter and it cleared first try. Switched back to Monk, retried same path I went with my Hunter, and quest still does not complete.
Side note: Can Loudmouth throw us back to the starting platform if we land on the platform but fail to meet the objective? Running back over and over is very time consuming compared to similar quests.